Heinrich von der linde



NITED STATES PATENT IFFICE.

HEINRICH VON DER LINDE, OF CREFELD, GERMANY.

SPECIFICATION forming part of Letters Patent No. 612,250, dated October 11, 1898 Application filed November 19, 1897. Serial No. 659,171. (No specimens.)

To aZZ whont itflncty concern:

Be it known that I, HEINRICH VON DER LINDE, a subject of the German Emperor, and a resident of Orefeld, in the Kingdom of Prussia and German Empire, haveinvented a certain new and useful Improved Process for the Electrolytic Separation of Metals, of which the following is a specification.

Heretofore the removal of plating from articles made of iron, so as to leave the iron unaffected and suitable for further use and mechanical working, has only been possible where the plating metal was tin. In such a case the removal of the tin-plating can be accomplished by electrolysis with the aid of a bath of soda-lye. In regard to other metals used for platingsuch as nickel, copper, or alloys of nickel and copperit has heretofore been impossible to employ an analogous process, as soda-lye is not applicable and there was no other means known whereby under the action of the electric current the plating metal could be dissolved without affecting theiron. In consequence the treatment of scraps or of used-up articles made of iron and plated with nickel has been such that the plating substance as well as the iron were dissolved and the more valuable plating metal was precipitated, while the remaining solution was used in the production of salts of iron, such as vitriol. However,-this procedure is not a very profitable one, as vitriol or similar substances are not as valuable as the metallic iron, which can be converted into steel or otherwise utilized.

The object of the present invention is a process for removing plating of a metal forming a soluble carbonate from articles made of iron, wherein only the metal forming the plating substance-such as nickel, copper, or alloys of copper and nickelare dissolved, while the iron is not affected.

The process consists in employing the plated articles as anodes in a bath containing ammoniu n1 carbonate in solution and in employing as the cathode the same metal of which the plating is made. When in this manner the plated articles are subjected to the actions of the electric, current, the metal separated from the anode is precipitated upon the cathode in metallic form where alloys of copper and nickel form the plating substance.

The essential feature of the above-described process is that the ammonium carbonate under the action of the electric current serves as solvent of the metal forming the plating without afiecting the iron and that from the solvent the metal which is being dissolved is simultaneously precipitated. It is further a novel feature that ammonium carbonate is employed with the aid of the electric current in dissolving the solid and continuous metals embodied in manufactured articles.

It has repeatedly been proposed to employ ammonium carbonate as solvent for oxids of different metals and for metals reduced from the ores but appearing in rawand non-compact condition. of 1895, United States Patent No. 272,391, and German Patent No. 29,900.) When these processes were employed, there were generally large quantities of oxids present. The ammonium carbonate mixed with ammonia was then used as the electrolyte and the metal was not compact and continuous, as in alloys, which are particularly difficult to affect. I-Ieretofore it has not been known that ammonium carbonate without the addition of ammonia under the action of the electric current is capable of dissolving solid compact metals forming continuous plating in such manner as to leave the iron unaffected and at the same time so cleaning it (which is not possible when ammonia is employed at the same time) that it maybe further treated in a metallurgical process, nor has there heretofore been a process known whereby plating consisting of nickel, copper, or alloy of copper and nickel could be removed from iron without dissolving the iron.

I claim-- 1. A process for removing the plating from articles made of iron for the purpose of making the remaining iron capable of being used in the manufacture of steel consisting in subjecting articles of iron which are plated with a solid coating of a metal forming a soluble carbonate as nickel, and employed as anodes in a depositing-cell, to the action of an electric current in a bath of ammonium carbonate, whereby the metal forming the plating (See British Patent No. 19,934

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isdissolved and is precipitated upon the oathode While the iron remains unaffected.

2. The improvement in the art of removing a solid compact metal forming a soluble carbonate from another metal consisting in using in a depositing-cell a bath of ammonium carbonate, placing the combined metals to be separated in said cell as the anode, and with a suitable cathode, and passing a current through the cell sufficient to separate one of 10 said metals leaving the other metal undissolved.

Signed at Orefeld, Germany, this 5th day of November, 1897.

HEINRICH VON DER LINDE. Witnesses:

GEORGE GOMPERTZ, CHARLES JoNAs. 

